Tritium can be made in production nuclear reactors, i.e., reactors designed to optimize the generation of tritium and special nuclear materials such as plutonium-239. Tritium is produced by neutron absorption of a lithium-6 atom.

Studies have not shown health effects at a chronic exposure below about 100 mSv. The regulatory public dose limit of 1 mSv is equivalent to 1% of this amount. Small amounts of tritium are released to the environment mostly from reactor operation and maintenance and during the manufacture of tritium light sources.

Cancer is the main risk from humans ingesting tritium. When tritium decays it spits out a low-energy electron (roughly 18,000 electron volts) that escapes and slams into DNA, a ribosome or some other biologically important molecule.

Nuclear weapons. Tritium is an important component in nuclear weapons. It is used to enhance the efficiency and yield of fission bombs and the fission stages of hydrogen bombs in a process known as “boosting” as well as in external neutron initiators for such weapons.

15 years

When tritium decays, it changes into an isotope known as helium-3. This decay process changes about 5.5 percent of the tritium into helium-3 every year.

Radium dials usually lose their ability to glow in the dark in a period ranging anywhere from a few years to several decades, but all will cease to glow at some point. A radium dial clock from the 1930s. A key point to bear in mind is this: the dial is still highly radioactive.

phosphorescent

Radium now has few uses, because it is so highly radioactive. Radium-223 is sometimes used to treat prostate cancer that has spread to the bones. Radium used to be used in luminous paints, for example in clock and watch dials.

Radium emits energy in the form of alpha particles and gamma rays, and will also decay to form radon. Radium in drinking water is of primary concern because this radiation may cause cancer, kidney damage and birth defects.